The closed vapor cycle engine offers advantages over a conventional internal combustion engine, particularly in regard to fuel conservation and atmospheric pollution. Vapor cycle engines serve well as bottoming cycle engines, such as one which utilizes the otherwise waste heat of an internal combustion engine. Also, they offer possible replacements for gasoline and deisel engines.
Trifluoroethanol (CF.sub.3 CH.sub.2 OH) and trifluroethanol/water working fluids are thermodynamically well suited for vapor cycle engines. These working fluids are less corrosive to iron alloys than water, and generally are not likely to cause early corrosion failure of engine parts. However, they are corrosive enough to be contaminated by corrosion products when in contact with carbon steel, cast iron and other iron alloy engine parts. These corrosion products are removed by filtration.